This paper summarizes recent advances on InAs/InP quantum dash (QD) materials for lasers and amplifiers, and QD device performance with particular interest in optical communication. We investigate ...both InAs/InP dashes in a barrier and dashes in a well (DWELL) heterostructures operating at 1.5 mum. These two types of QDs can provide high gain and low losses. Continuous-wave (CW) room-temperature lasing operation on ground state of cavity length as short as 200 mum has been achieved, demonstrating the high modal gain of the active core. A threshold current density as low as 110 A/cm super(2) per QD layer has been obtained for infinite-length DWELL laser. An optimized DWELL structure allows achieving of a T sub(0) larger than 100 K for broad-area (BA) lasers, and of 80 K for single-transverse-mode lasers in the temperature range between 25degC and 85degC. Buried ridge stripe (BRS)-type single-mode distributed feedback (DFB) lasers are also demonstrated for the first time, exhibiting a side-mode suppression ratio (SMSR) as high as 45 dB. Such DFB lasers allow the first floor-free 10-Gb/s direct modulation for back-to-back and transmission over 16-km standard optical fiber. In addition, novel results are given on gain, noise, and four-wave mixing of QD-based semiconductor optical amplifiers. Furthermore, we demonstrate that QD Fabry-Perot (FP) lasers, owing to the small confinement factor and the three-dimensional (3-D) quantification of electronic energy levels, exhibit a beating linewidth as narrow as 15 kHz. Such an extremely narrow linewidth, compared to their QW or bulk counterparts, leads to the excellent phase noise and time-jitter characteristics when QD lasers are actively mode-locked. These advances constitute a new step toward the application of QD lasers and amplifiers to the field of optical fiber communications
High-speed photodiodes are a key element of numerous photonic systems. With the development of potential applications in the THz range such as sensing, spectroscopy, and wireless transmission, ...devices with integrated antenna covering the frequency range from 0.1 to 3 THz will become essential. In this paper, we discuss the development of uni-traveling carrier photodiodes with integrated antennas to address that need. In particular we develop the key elements to present a simple design tool for the efficient integration of the device with an antenna. We also present fabricated device results that show the highest figure of merit to date for photonic THz emitters. When integrated with well-matched antennas the devices have achieved record level of power up to 1 THz compared to other published photomixers. We also show that these devices can be used as receivers at frequencies up to 560 GHz with conversion losses of the order of 30 dB.
We have developed a high-performance uni-traveling-carrier (UTC) and a modified uni-traveling-carrier (MUTC) photodiode (PD). We report a comparison between the two devices comprising both a 1.5- ...μm-thick absorption layer followed by a 0.5-μm-thick transparent collector layer. Both devices showed simultaneously a high responsivity (larger than 0.92 A/W at 1.55 μm), a high saturation current (larger than 100 mA at 10 GHz), and a high linearity (OIP3 of 35 dBm at 10 GHz). Thanks to a partly depleted absorber, the MUTC-PD is demonstrated to achieve a higher bandwidth (more than 20 GHz at high current), while the UTC-PD is demonstrated to achieve a higher saturation current and a less voltage dependent radio-frequency and linearity characteristics.
High power Semiconductor Optical Amplifiers (SOA) are often integrated in optical systems such as mode locked lasers, hybrid, or monolithically integrated Master Oscillator Power Amplifiers (MOPA) ...for applications such as LIDAR systems or free space optical communications. Both these applications require high power and signal modulation, either for data transmission or specific LIDAR adapted signals, which can be provided by either modulating the amplitude of the seed laser or using an external modulator. It is also possible to directly modulate the gain of the SOA by modulating the input current. However, as the input power of the SOA is often high in these configurations (around 1 mW), it operates under the saturation regime. In this article, we present an experimental study of the dynamic characteristics of a two-section high power SOA. DC characteristics for different pump current pairs are measured. The S21 parameter is measured, and a model is proposed to understand and predict the dynamic response of the SOA. The impact of the gain saturation with regards to input power on the behavior of the SOA is investigated by pumping the two sections with different current values. Extinction ratio and eye diagrams are measured in three different configurations with the modulation applied on a seed DFB laser, on the input section, then on the output section of the SOA at 1 Gbps, 2.5 Gbps, and 5 Gbps.
We report a new scheme of photonic microwave oscillator at telecommunication wavelength. It consists of two monolithic distributed feedback (DFB) laser diodes, whose beat-note is stabilized by means ...of frequency-shifted optical feedback. The feedback beam is modulated by the delayed beat-note itself, and this permits to get a stable optically carried microwave without the need of any external reference. Dual and single sideband modulation schemes were tested by using an intensity modulator and a frequency shifter, respectively. The single sideband scheme results in a better stability and a 10 dB improvement of the phase noise. A phase noise level of -65 dBc/Hz, detection limited, at 100 Hz from a 12 GHz carrier is obtained.
We present a photonically-excited antenna array at E-band for scanning by beam switching in wireless links. First, we discuss the proposed technique applied to photonic-enabled (sub)millimeter-wave ...transmitters. Next, we present our implementation; it consists of two sub-arrays of stacked patches as primary feeds of a Polytetrafluoroethylene (PTFE) lens, with one photodiode feeding each sub-array. To validate the assembly, the return loss and radiation patterns have been measured for one of the sub-arrays excited with a coplanar probe. In turn, the lens illuminated by one of the sub-arrays yields a directivity of 27 dBi. The radiation patterns measured for the transmitter module (including the lens) are in very good agreement with full-wave simulations, and they show that excitation of one of either sub-arrays allows beam switching between <inline-formula><tex-math notation="LaTeX">\pm 2.7^\circ</tex-math></inline-formula> with a beam crossover at <inline-formula><tex-math notation="LaTeX">-3\, \mathrm{dB}</tex-math></inline-formula>. Finally, we have tested the transmitter in a 0.6 m wireless link. Depending on the position of the detector and on which sub-array is excited, we have accomplished 5 Gbps transmission for on-off-keying modulation and direct detection (BER <inline-formula><tex-math notation="LaTeX">=10^{-11}</tex-math></inline-formula>). The system constitutes an initial proof of photonic-assisted beam switching for mm-wave transmitters enabling broadband operation with a directive and switchable beam.
This paper reviews the current state of the art of photonic-enabled generation of radio-frequency signals with frequencies within the millimeter wave range (30 to 300 GHz) and above using ...photonic-integrated circuits (RF-PICs). One of the most important applications to date is the generation of carrier wave frequencies for ultrabroadband wireless communications systems, with data rates up to 100 Gb/s. Among the different photonic signal generation techniques that are available, we focus on the approaches for which photonic integrated solutions have been explored. Optical heterodyning is first presented, based on achieving the integration of a dual wavelength sources. The second approach is through onchip integrated mode locked lasers, with excellent performance in terms of frequency stable, low phase-noise narrow linewidth sources. We review the different laser structures that have been reported, to support the advantages of the new structures that we propose.
A monolithically integrated photonic source for tuneable mm-wave signal generation has been fabricated. The source consists of 14 active components, i.e. semiconductor lasers, amplifiers and ...photodetectors, all integrated on a 3 mm(2) InP chip. Heterodyne signals in the range between 85 GHz and 120 GHz with up to -10 dBm output power have been successfully generated. By optically injection locking the integrated lasers to an external optical comb source, high-spectral-purity signals at frequencies >100 GHz have been generated, with phase noise spectral density below -90 dBc/Hz being achieved at offsets from the carrier greater than 10 kHz.
The letter presents a fabrication platform based on silicon nitride embedded in silica on silicon wafers. Long Bragg gratings have been fabricated for narrow linewidth lasers. A narrow stop-band (0.2 ...nm) Bragg grating with etched facet chips is achieved in this platform. Heaters have been integrated on the chips allowing tuning of the Bragg wavelength over 1.5 nm. Lasers have been obtained and tested by butt-coupling of one of these Bragg gratings to a reflective semiconductor optical amplifier (R-SOA). On these laser cavities, we obtained a continuous tuning range of 0.16 nm and a discontinuous tuning range of 1.5 nm.
Generation of optical frequency combs (OFC) using semiconductor laser sources has been an active research topic for years, since they offer good performances for many applications without the bulky ...and expensive aspects of ion doped fiber or crystal based laser sources. In this paper, we demonstrate the generation of low free spectral range mode-locked laser using hybrid III-V/Si 3 N 4 butt coupling. We start by describing the design and the fabrication process of the active R-SOA chip made at our laboratory, and the passive Si 3 N 4 chip having low losses measured to be around 6 dB/m. We then report the integration process and the results of passive mode locking. Our mode-locked laser has a repetition rate of 360 MHz, which is, to the best of our knowledge, the lowest repetition rate achieved for a hybrid integrated mode-locked laser. The frequency comb generated has a 30 dB bandwidth of 2.8 nm (349 GHz). Finally, we show the demonstration of active and harmonic mode locking up to the sixth harmonic.
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